Introduction
A cache utilizes the RAM of your computer to store and serve frequently accessed data from backend systems like databases. As a result, a caching layer improves performance, minimizes costs, and reduces the load on a database.
The Redis in-memory database server is a suitable caching application because it requires minimal setup and scales well in a production environment. When you implement a cache, your application first queries Redis to get data. If the cache is empty, the application fetches data from the database. Then, it creates a cache for future queries. This in-memory caching solution is several times faster when compared to rotating or modern Solid State Disks (SSD).
This guide walks you through the process of implementing a caching layer with Redis to speed up MongoDB queries using the Go programming language.
Prerequisites
Deploy an Ubuntu 20.04 server.
Create a non-root sudo user.
Install and configure a MongoDB server.
Set up a Redis server.
Download and install the Go programming language.
1. Set Up a Sample Database
This guide uses a sample MongoDB database to store data permanently on a disk. Follow the steps below to create the database.
Log in to your MongoDB server. Replace mongo_db_admin with the correct user account.
$ mongosh -u mongo_db_admin -p --authenticationDatabase admin
Enter your password to proceed.
Run the statement below to create an e-commerce database.
test> use e-commerce
Output.
switched to db e-commerce
Insert five documents into a new products collection.
e-commerce> db.products.insertMany([
{"product_id" : 1,
"product_name" : "INSTANT WATER HEATER",
"retail_price" : 45.55
},
{"product_id" : 2,
"product_name" : "DOUBLE SOCKET WITH PATTRESS",
"retail_price" : 6.65
},
{"product_id" : 3,
"product_name" : "80MM USB PRINTER",
"retail_price" : 125.95
},
{"product_id" : 4,
"product_name" : "FITNESS SMARTWATCH",
"retail_price" : 39.85
},
{"product_id" : 5,
"product_name" : "3.1A FAST CHARGER",
"retail_price" : 23.90
}
]);
Output.
{
acknowledged: true,
insertedIds: {
'0': ObjectId("625d2694dd1d8bd34f469875"),
'1': ObjectId("625d2694dd1d8bd34f469876"),
'2': ObjectId("625d2694dd1d8bd34f469877"),
'3': ObjectId("625d2694dd1d8bd34f469878"),
'4': ObjectId("625d2694dd1d8bd34f469879")
}
}
Querying the products collection to verify the documents.
e-commerce> db.products.find()
Output.
[
{
_id: ObjectId("625d2694dd1d8bd34f469875"),
product_id: 1,
product_name: 'INSTANT WATER HEATER',
retail_price: 45.55
},
{
_id: ObjectId("625d2694dd1d8bd34f469876"),
product_id: 2,
product_name: 'DOUBLE SOCKET WITH PATTRESS',
retail_price: 6.65
},
{
_id: ObjectId("625d2694dd1d8bd34f469877"),
product_id: 3,
product_name: '80MM USB PRINTER',
retail_price: 125.95
},
{
_id: ObjectId("625d2694dd1d8bd34f469878"),
product_id: 4,
product_name: 'FITNESS SMARTWATCH',
retail_price: 39.85
},
{
_id: ObjectId("625d2694dd1d8bd34f469879"),
product_id: 5,
product_name: '3.1A FAST CHARGER',
retail_price: 23.9
}
]
Log out from the MongoDB database.
e-commerce> quitCreate the main.go File
The main.go file is the entry point in this sample application. This file contains the main(...){...} function that fires when your application starts. Execute the steps below to set up the file.
Create a new directory for your project. This approach keeps your project organized and avoids conflicting your source code with the rest of the Linux files.
$ mkdir project
Switch to the new project directory.
$ cd project
Open a new main.go file in an editor.
$ nano main.go
Enter the following information into the file. Replace mongo_db_admin and EXAMPLE_PASSWORD with the correct account details for the MongoDB server.
package main
import (
"context"
"encoding/json"
"fmt"
"net/http"
)
const (
MONGO_DB_USER = "mongo_db_admin"
MONGO_DB_PASS = "EXAMPLE_PASSWORD"
MONGO_DB_NAME = "e-commerce"
)
func main() {
http.HandleFunc("/products", requestHandler)
http.ListenAndServe(":8080", nil)
}
func requestHandler(w http.ResponseWriter, req *http.Request) {
w.Header().Set("Content-Type", "application/json")
var respMessage map[string]interface{}
var respErr error
ctx := context.Background()
isCached, productsCache, err := getFromCache(ctx)
if err != nil {
respErr = err
} else {
if isCached == true {
respMessage = productsCache
respMessage["_source"] = "Redis Cache"
} else {
respMessage, err = getFromDb(ctx);
if err != nil {
respErr = err
}
err = addToCache(ctx, respMessage)
if err != nil {
respErr = err
}
respMessage["_source"] = "MongoDB database"
}
}
if respErr != nil {
fmt.Fprintf(w, respErr.Error())
} else {
enc := json.NewEncoder(w)
enc.SetIndent("", " ")
if err := enc.Encode(respMessage); err != nil {
fmt.Fprintf(w, err.Error())
}
}
}Save and close the file.
In the above file, you're creating an HTTP server that listens for incoming connections on port 8080.
In the main(...){...} function, you're redirecting incoming requests to the requestHandler(...){...} function. Under this function, you're using the isCached, productsCache, err := getFromCache(ctx) statement to retrieve products from a Redis Cache. In case the cache is empty, you're fetching the data from the MongoDB database using the statement respMessage, err = getFromDb(ctx);.
Then, you're outputting the products' data in a JSON format. You're also appending a _source attribute to mark the data source. That is, either from the cache or the database.